Incomplete spinal cord injury (SCI) may result in muscle weakness and difficulties with force gradation. Although these impairments arise from the injury and subsequent changes at spinal levels, changes have also been demonstrated in the brain. Blood-oxygen-level dependent (BOLD) imaging was used to investigate these changes in brain activation in the context of unimanual contractions with the first dorsal interosseous muscle. BOLD- and force data were obtained in 19 individuals with SCI (AISA Impairment Scale [AIS] C/D, level C4–C8) and 24 able-bodied controls during maximal voluntary contractions (MVCs). To assess force modulation, participants performed 12 submaximal contractions with each hand (at 10, 30, 50, and 70% MVC) by matching their force level to a visual target. MVCs were weaker in the SCI group (both hands p < 0.001), but BOLD activation did not differ between SCI and control groups. For the submaximal contractions, force (as %MVC) was similar across groups. However, SCI participants showed increased activity of the ipsilateral motor cortex and contralateral cerebellum across all contractions, with no differential effect of force level. Activity of ipsilateral M1 was best explained by force of the target hand (vs. the non-target hand). In conclusion, the data suggest that after incomplete cervical SCI, individuals remain capable of producing maximal supraspinal drive and are able to modulate this drive adequately. Activity of the ipsilateral motor network appears to be task related, although it remains uncertain how this activity contributes to task performance and whether this effect could potentially be harnessed to improve motor functioning.

中文翻译：

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脊髓不完全损伤后同侧 M1 激活增加有助于运动表现

不完全性脊髓损伤 (SCI) 可能导致肌肉无力和力量分级困难。尽管这些损伤是由脊髓水平的损伤和随后的变化引起的，但大脑中也出现了变化。血氧水平依赖 (BOLD) 成像用于研究在第一骨间背侧肌肉单手收缩的情况下大脑激活的这些变化。在最大自主收缩 (MVC) 期间，在 19 名 SCI 患者（AISA 损伤量表 [AIS] C/D，C4-C8 级）和 24 名健全对照中获得了 BOLD 和力数据。为了评估力量调节，参与者通过将他们的力量水平与视觉目标相匹配，用每只手（在 10、30、50 和 70% MVC）进行 12 次次最大收缩。SCI 组的 MVC 较弱（双手p < 0.001），但 BOLD 激活在 SCI 和对照组之间没有差异。对于次最大收缩，各组的力（如 %MVC）相似。然而，SCI 参与者在所有收缩中表现出同侧运动皮层和对侧小脑的活动增加，而力量水平没有差异效应。同侧 M1 的活动最好用目标手（与非目标手）的力量来解释。总之，数据表明，在不完全颈椎 SCI 后，个体仍然能够产生最大的脊髓上驱动力，并且能够充分调节这种驱动力。同侧运动网络的活动似乎与任务相关，尽管尚不确定该活动如何促进任务执行以及是否可以利用这种影响来改善运动功能。